1. Field of the Invention
The present invention relates to a so-called projector-type vehicle headlamp.
2. Description of the Related Art
In general, the projector-type vehicle headlamp is configured so that a projection lens is disposed on an optical axis extending in the longitudinal direction of a vehicle, a light source is disposed on a rear side of a rear side focal point of the projection lens, and light from the light source is reflected by a reflector toward the optical axis.
In this respect, JP-A-2003-16813 discloses a projector-type vehicle headlamp having a pair of cylindrical lenses in which the cylindrical lenses are respectively disposed at the left and right sides of the projection lens and a part of the reflection surface of the reflector is formed as a reflection surface for reflecting light toward the respective cylindrical lenses.
In the normal projector-type vehicle headlamp, a distribution light pattern formed by irradiated light thereof is produced as an inverted projection image of an light source image which is formed on the rear side focal point surface of a projection lens by light emitted from a light source and reflected by a reflector. Thus, it is not easy to enlarge the size of the distribution light pattern or to increase the luminance at the center portion of the distribution light pattern.
In this respect, when the vehicle head lamp is configured so that a pair of cylindrical lenses are respectively disposed at the left and right sides of the projection lens, as disclosed in JP-A-2003-16813, it becomes possible to set the shape of the distribution light pattern so that it has large left and right diffusion angles. Further, the luminance at the center portion of the distribution light pattern can be increased by disposing a suitable auxiliary lens in place of these cylindrical lenses.
However, in this case, since it is necessary that the part of the reflection surface of the reflector is formed as a reflection surface for reflecting light toward the respective cylindrical lenses (or another auxiliary lens), there arises a problem that the configuration or the lamp is complicated. Further, the distribution light pattern formed by the irradiation light from the vehicle headlamp is configured as a composite distribution light pattern, which is the composition of a basic distribution light pattern formed by light irradiated in the forward direction via the projection lens and auxiliary distribution light patterns formed by light in the forward direction via the respective cylindrical lenses (or another auxiliary lens). In this case, since the basic distribution light pattern and the auxiliary distribution light patterns are formed by independent optical systems, respectively, there also arises a problem that the light distribution likely becomes non-uniform.